Usb Functional Description In Peripheral Mode; Srp-Capable Peripheral; Peripheral States - ST STM32F40 Series Reference Manual

RM0090
order to save power. The A-device is always in charge of driving V
OTG_HS role (host or peripheral). The SRP A/B-device program model is described in detail
in Section 31.13: OTG_HS programming
31.5

USB functional description in peripheral mode

The OTG_HS operates as an USB peripheral in the following circumstances:
●
OTG B-device
OTG B-device default state if the B-side of USB cable is plugged in
●
OTG A-device
OTG A-device state after the HNP switches the OTG_HS to peripheral role
●
B-Device
If the ID line is present, functional and connected to the B-side of the USB cable, and
the HNP-capable bit in the Global USB Configuration register (HNPCAP bit in
OTG_HS_GUSBCFG) is cleared (see On-The-Go specification Revision 1.3 section
6.8.3).
●
Peripheral only (see
The force peripheral mode bit in the Global USB configuration register (FDMOD in
OTG_HS_GUSBCFG) is set to 1, forcing the OTG_HS core to operate in USB
peripheral-only mode (see On-The-Go specification Revision 1.3 section 6.8.3). In this
case, the ID line is ignored even if it is available on the USB connector.
Note: To build a bus-powered device architecture in the B-Device or peripheral-only configuration,
an external regulator must be added to generate the V
31.5.1

SRP-capable peripheral

The SRP capable bit in the Global USB configuration register (SRPCAP bit in
OTG_HS_GUSBCFG) configures the OTG_HS to support the session request protocol
(SRP). As a result, it allows the remote A-device to save power by switching V
the USB session is suspended.
The SRP peripheral mode program model is described in detail in
session request
31.5.2

Peripheral states

Powered state
The V
BUS
Powered state (see USB2.0 specification section 9.1). The OTG_HS then automatically
connects the DP pull-up resistor to signal full-speed device connection to the host, and
generates the session request interrupt (SRQINT bit in OTG_HS_GINTSTS) to notify the
Powered state. The V
during USB operations. If V
because power disturbances occurred or the host port has been switched off), the OTG_HS
automatically disconnects and the session end detected (SEDET bit in
OTG_HS_GOTGINT) interrupt is generated to notify that the OTG_HS has exited the
Powered state.
Figure 359: USB peripheral-only
protocol.
input detects the B-session valid voltage used to put the USB peripheral in the
input also ensures that valid V
BUS
BUS
Doc ID 018909 Rev 4
USB on-the-go high-speed (OTG_HS)
model.
drops below the B-session valid voltage (for example
regardless of the
BUS
connection)
supply voltage from V
DD
Section : B-device
levels are supplied by the host
BUS
.
BUS
off when
BUS
1164/1422